This invention relates to a method of purifying exhaust gas from an internal combustion engine which is mainly used as a prime mover for a small generator, industrial machines, or the like and has a short exhaust system, and to an apparatus therefor.
An apparatus for purifying exhaust gas which uses a three way conversion (hereinafter called TWC) catalyst is conventionally and commonly used in automobiles. This apparatus works effectively in an internal combustion engine in which the air/fuel ratio is highly accurately controlled to a theoretical air/fuel ratio, i.e., to a neighbourhood of A/F=14.6 using an O.sub.2 sensor. However, it cannot fully perform its capability in an internal combustion engine in which the air/fuel ratio is not highly accurately controlled.